In an exhaust gas recirculation cooler, the exhaust gas is cooled which is subsequently again fed to combustion chambers of an internal combustion engine together with the combustion air. In particular, the exhaust gas recirculation coolers are employed in motor vehicles with diesel engines in order to reduce exhaust gas emissions by recirculating the cooled exhaust gas into the combustion chambers.
For cooling the exhaust gas, a plurality of cooling tubes is arranged in a plurality of rows in a housing to form a tube bundle. The cooling tubes are mostly winglet tubes formed from stainless steel, in which flow obstructions for better heat transfer are integrally formed—for example by impressing. The exhaust gas flows through the winglet tubes and is cooled by a coolant flowing in the housing. An exhaust gas inlet and an exhaust gas outlet are generally accomplished by a diffuser, wherein the respective diffuser is connected to the housing and forms an interface to the customer connection.
Such exhaust gas recirculation coolers are known for example from DE 196 54 366 A1, DE 199 61 284 A1, DE 10 2007 005 370 A1, DE 10 2009 038 643 A1, DE 10 2010 001 635 A1, DE 10 2010 008 176 B4, DE 11 2013 004 680 T5, US 2013/0 327 499 A1, DE 10 2014 208 259 A1 and US 2015/0 260 466 A1.
In order to achieve a better heat transfer between the exhaust gas and the coolant, a longer and even exposure of the tube bundle to the coolant is aimed at. However since the quantity of the inflowing coolant is limited, a longer and even exposure of the tube bundle to the coolant in the conventional exhaust gas recirculation cooler is difficult to achieve.